1. Field of the Invention (Technical Field)
The invention relates to a system and method for erecting an engineered, composite structural assembly suitable for residential or commercial buildings.
2. Background Art
One of mankind's most longstanding needs, and one to which enormous effort has been devoted over time, is the need for inexpensive yet adequate shelter from the elements. While developments in structural and materials engineering, architecture, and construction financing have improved the speed, efficiency, and cost-effectiveness of residential and commercial/industrial building, a need remains for a system of building construction, particularly residential construction, that is comparatively inexpensive, quick, and makes expanded use of renewable resources. In recent years particularly, increased focus has been placed on the need to develop construction methods and materials that minimize impacts on energy demands and environmental quality. Among other concerns are a wide-felt demand for buildings and dwellings that are energy-efficient, thereby reducing demand on energy sources, especially the non-renewable fossil fuels resources. Similarly, there is a heightened awareness of the importance of maximizing the use of readily renewable sources of construction materials.
Straw is a simple, inexpensive, widely available, renewable resource that for centuries has seen application in the art of building construction. Straw has been a binding, reinforcing, and insulating agent in mud-brick and adobe construction since prehistoric times. Houses constructed from compressed organic matter are still used today, and were commonly found in the embodiment of the "sod" houses of the midwestern United States during the nineteenth century.
More recently, the possibility of expanding the use of straw and other fibrous organics beyond their traditional role has received attention in the art. Use of straw as a primary, rather than ancillary, construction material presents recognized advantages. Straw or other shredded material, when bound into bales and stacked to form walls and roofs, offers desirable structural characteristics of low weight, corrosion and rust resistance, very high insulation value, and versatility. Additionally, straw as a primary construction material is economical and widely available. Moreover, straw comprises a renewable natural resource that presently is mostly wasted--making it attractive from an environmental, as well as economical, standpoint.
U.S. Pat. No. 225,065 to Leeds, entitled Building Houses, Barns, Fences, & c., discloses a mode of erecting structures, consisting of stacking baled matter within wooden corner posts and capping them with wooden planks. No surface coating or finishing is suggested.
U.S. Pat. No. 312,375 to Orr, entitled Wall of Buildings and Other Structures, discloses a system for erecting walls consisting of stacked bales of material, the bales being compressed vertically between screw-actuated compression plates at the top and bottom of the walls. No rigid framework or support system, temporary or permanent, is disclosed.
U.S. Pat. No. 801,361 to Clayton, et al., entitled Composite Building Structure, teaches the formation of walls and roofs fashioned from concrete shells. The shells are parallelly spaced by concrete webs perpendicularly disposed between the shells to form discrete cells, which cells are filled with baled or compressed straw. The assembly evidently purports to be self-supporting during construction, or is pre-constructed in modules and then stacked, as no framework or temporary support system is disclosed.
U.S. Pat. No. 1,604,097 to Hewlett, entitled Wall Structure, shows a construction system using fibers coated with a binding agent which are tamped into a mold and allowed to dry to form a rigid, yet light and porous, building block. The rigid blocks are then stacked to form a wall, and include holes therethrough to serve, when aligned into vertical "passageways," as molds for poured concrete columns. As disclosed, the system requires the manufacture of individual blocks by mixing the binding agent with the fibrous material to exacting specifications to form what is, essentially, a type of brick.
U.S. Pat. No. 1,633,702 to Hewlett, et al., entitled Building Structure, discloses a variation on the invention of the '097 patent to Hewlett.
U.S. Pat. No. 4,301,198 to Prior, entitled Building Component and Method of Making the Same, shows a system for making building components consisting of a rigid form or mold filled with shredded material and coated with a plastic or resinous "skin."
Previous efforts to adapt straw-bale construction methods to modern, conventional, building needs have been hampered by structural limitations. Some of the advantages of straw bales (e.g. reduced weight, low-density) also present limitations to structural strength. Baled straw is very compressible and comparatively lightweight and flexible; consequently, a straw bale cannot merely be treated as just another type of brick for building purposes. Walls composed of straw bales must be supplied with reinforcing features to add stability and load-bearing capabilities.
Additionally--and especially since the nature of straw bales prohibits their being securely mortared together at their joints to form a monolithic wall--some means must be provided to add tensile and compressive strength to a straw-bale wall, especially at its interior and exterior faces where bending moment stresses are at their maximum. Merely coating the faces of a straw-bale wall with a stiffening substance is insufficient to serve the latter function; without effective means for transferring shear forces between the respective faces, the faces will act independently, severely reducing the wall's effective moment of inertia. Also, most baled-fiber wall systems must be adequately and temporarily supported and stabilized during erection, when wind loads and other perturbations can easily upset an entire wall. The present invention addresses these and other shortcomings of the methods of the prior art.